Qualitative behaviour of viscoplastic solutions in the vicinity of maximum-friction surfaces

The maximum-friction surface is a source of singular solution behaviour for several rate-independent plasticity models. Solutions based on conventional viscoplastic models do not show such behaviour. For a class of materials, there is a range of temperatures and/or strain rates where a necessity of the consideration of rate effects depends on the area of application of the final result. Hence, the same material under the same conditions can be represented by either rate-independent or rate-dependent models. In this case, a reasonable requirement is that viscous effects should not be very significant and, in particular, the qualitative behaviour of viscoplastic solutions should be similar to that of solutions based on rate-independent models. The present paper deals with this issue by means of the solution for simultaneous shearing and expansion of a hollow cylinder under plane-strain deformation. One of the goals of the paper is to show that there is a class of viscoplastic models satisfying the requirement formulated. The other goal is to find an asymptotic representation of the solution in the vicinity of the maximum-friction surface and compare it with the rigid perfectly plastic solution.     

4H-SiC混合PN/Schottky二极管的研制

报道了4H-SiC混合PN/Schottky二极管的设计、制备和特性．该器件用镍作为肖特基接触金属,使用了结终端扩展（JTE）技术．在肖特基接触下的n型漂移区采用多能量注入的方法形成P区而组成面对面的PN结,这些PN结将肖特基接触屏蔽在高场之外,离子注入的退化是在1500℃下进行了30min．器件可耐压600V,在600V时的最小反向漏电流为1×10-3A/cm2．1000μm的大器件在正向电压为3V时电流密度为200A/cm2,而300μm的小尺寸器件在正向电压为3.5V电流密度可达1000A/cm2．     

Predicting rice phenotypes with meta and multi-target learning

Machine Learning - The features in some machine learning datasets can naturally be divided into groups. This is the case with genomic data, where features can be grouped by chromosome. In many...     

Thin-Film Baroresistors Based on Sm1 – xGdxS Solid Solutions

Semiconductors - The effect of the Gd concentration on the temperature and pressure coefficients of the resistance of thin polycrystalline films of Sm1 – xGdxS solid solutions, where x = 0,...     

Crystalline quality improvement in silicon films on sapphire using recrystallization from the silicon-sapphire interface

The use of the process of solid-phase recrystallization reduces to a great extent the number of defects in the silicon layer. An amorphous layer was formed by implantation of silicon ions. The crystalline quality of the SOS structures has been assessed by the method of high-resolution double-crystal X-ray diffraction. Silicon layers with a thickness d = 1000–2500 Å and a high crystalline quality have been obtained after implantation of 150-keV silicon ions with subsequent high-temperature annealing.

     

Exploring three-dimensional matrix-assisted laser desorption/ionization imaging mass spectrometry data: three-dimensional spatial segmentation of mouse kidney

Three-dimensional (3D) imaging has a significant impact on many challenges of life sciences. Three-dimensional matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) is an emerging label-free bioanalytical technique capturing the spatial distribution of hundreds of molecular compounds in 3D by providing a MALDI mass spectrum for each spatial point of a 3D sample. Currently, 3D MALDI-IMS cannot tap its full potential due to the lack efficient computational methods for constructing, processing, and visualizing large and complex 3D MALDI-IMS data. We present a new pipeline of efficient computational methods, which enables analysis and interpretation of a 3D MALDI-IMS data set. Construction of a MALDI-IMS data set was done according to the state-of-the-art protocols and involved sample preparation, spectra acquisition, spectra preprocessing, and registration of serial sections. For analysis and interpretation of 3D MALDI-IMS data, we applied the spatial segmentation approach which is well-accepted in analysis of two-dimensional (2D) MALDI-IMS data. In line with 2D data analysis, we used edge-preserving 3D image denoising prior to segmentation to reduce strong and chaotic spectrum-to-spectrum variation. For segmentation, we used an efficient clustering method, called bisecting k-means, which is optimized for hierarchical clustering of a large 3D MALDI-IMS data set. Using the proposed pipeline, we analyzed a central part of a mouse kidney using 33 serial sections of 3.5 μm thickness after the PAXgene tissue fixation and paraffin embedding. For each serial section, a 2D MALDI-IMS data set was acquired following the standard protocols with the high spatial resolution of 50 μm. Altogether, 512?495 mass spectra were acquired that corresponds to approximately 50 gigabytes of data. After registration of serial sections into a 3D data set, our computational pipeline allowed us to reveal the 3D kidney anatomical structure based on mass spectrometry data only. Finally, automated analysis discovered molecular masses colocalized with major anatomical regions. In the same way, the proposed pipeline can be used for analysis and interpretation of any 3D MALDI-IMS data set in particular of pathological cases.     

Ferrimagnetic Spin-Wave Resonance and Superconductivity in Carbon Nanotubes Incorporated in Diamond Matrix

The phenomenon of ferrimagnetic spin-wave resonance [uncompensated antiferromagnetic spin-wave resonance] has been detected for the first time. It has been observed in carbon nanotubes, produced by high-energy ion beam modification of diamond single crystals in 〈100〉 direction. Peculiarities of spin-wave resonance observed allow to insist on the formation in given nanotubes of s ⁺-superconductivity at room temperature, coexisting with uncompensated antiferromagnetic ordering.     

Metallurgical characterisations of CMSX-4 vacuum-brazed with BNi-2 and BNi-9

High temperature brazing of nickel-based superalloys often produces joints containing hard, brittle micro-constituents that can be detrimental to mechanical properties and challenging to characterise consistently. In this study, techniques including low angle micro-sectioning, image analysis with ImageJ and electron probe micro-analysis were used to determine the composition, hardness and dispersion parameters of phases in single crystal superalloy CMSX-4, vacuum furnace brazed with BNi-2 and BNi-9 filler metals (FMs). Both FMs produced similar joints with hard centreline eutectic phases, a soft isothermally solidified zone and boron diffusion-affected zone in the CMSX-4. The volume fraction, particle size distribution and inter-particle spacing data generated will provide a framework for future metallurgical characterisations and assist in the development of microstructure–mechanical property relationships.     

Thermodynamic and kinetic simulations of high temperature brazing: microstructure evolution in CMSX-4 joints

In this study, thermodynamic and kinetic simulations with Thermo-Calc and DICTRA software were utilised to predict the microstructural evolution observed in brazing of high-strength nickel base single crystal superalloy, CMSX-4, with two commonly used filler metals (FMs), AWS BNi-2 (AMS 4777) and AWS BNi-9. DICTRA diffusion models of the Ni-B binary system were used to calculate base materials dissolution, the amount of centreline eutectic constituents and time required for complete isothermal solidification at various joint gaps. Thermo-Calc simulations using the CALPHAD technique predicted transformation temperatures and equilibrium phases of the joints based on the chemical compositions of the two FMs. Experimental brazing and characterisations of joint microstructure at various brazing temperatures, hold times and joint gaps were used to validate the simulation modelling results. Good correlation with both Thermo-Calc and DICTRA simulations and empirical data demonstrated the benefits of using this modelling approach for braze joint development and applications.